Remove obsolete tests that were incorrectly resurrected during the

merge in 4c4eed3.

complex_expressionBUG was renamed back to complex_expression in
782449d, and the merge incorrectly kept
both copies.  The other 5 tests were deleted in
03f86af.

One other test (lowerboundBUG) was incorrectly resurrected during that
merge after it was deleted in 0398f04,
but it was later deleted again in
addfe37.

Author: mattmccutchen-cci